The drive power of the compressors may be considerably reduced by the intermediate cooling of the compressed medium in a compression process. The heat of the intercooler, which is to be removed, has usually been hitherto removed unused into the atmosphere.
A combined gas and steam power plant with a two-stage compressor for compressing the combustion air fed into the combustion chamber of the gas turbine is known from EP 0 597 305 B2. An intercooler, whose heat exchange surfaces are integrated in the water-steam circuit of the waste heat boiler arranged downstream of the gas turbine, is arranged between the two compressor stages. Feedwater, whose pressure was previously raised by a booster pump, is fed into the intercooler. The feedwater heated in the intercooler is fed to a steam collecting drum, in which it partially evaporates. The steam thus formed is introduced into the superheater, and the water is introduced into the mixed preheater. The principle of heat release is thus achieved by the re-evaporation of the cooling water being circulated in the drum. The extent of the heat release is thus strongly affected by the particular steam pressure in the drum.
The combined plant known from EP 0 597 305 B2 with the utilization of the waste heat of the compressor requires an additional booster pump for the cooling circuit besides the feedwater pump, which is present anyway. The waste heat of the compressor is utilized in the medium peculiar to the plant, namely, the compressed combustion air. Only the compressor heat that is generated in the intercooler is utilized.